The present invention relates to a cleaning blade for use with a photoelectronic (dry type) copying machine.
The residual toner on a photosensitive drum and a fixing drum (hereinafter referred to merely as a drum) of a photoelectronic copying machine has heretofore been wiped off by use of a cleaning web of fabric, brushed off by use of a cleaning brush made of pile yarn, or scraped off by use of a cleaning blade of rubber.
With a cleaning web, the drum is liable to suffer mechanical damage because the web is pressed hard against the drum. Further, since the cleaning web is usually housed rolled-up in the copying machine so as to shift the position in contact with the drum and the amount of the cleaning web housed in the machine is small because of limited space in the machine, the web has to be frequently replaced.
Though a cleaning brush is more commonly used, it is difficult to select a proper pile yarn for the brush in quality, hardness and quantity. Also, the cleaning brush tends to cause mechanical damage on the drum surface or cause it to be electrostatically charged owing to the friction, making it difficult to remove toner from the drum surface and thus deteriorating the performance of the drum. Further the cleaning brush itself wears rapidly and requires repeated replacements.
As for a cleaning blade, it is simple in mechanism and compact in size and thus most commonly used. But, with the blade made of a single material such as urethane rubber, neoprene rubber or silicone rubber, if the blade is pressed too hard against the drum, its edge will rapidly wear due to severe friction. If the pressure is too small, then toner will not be completely scraped off.
In order to improve the lubricating properties of the cleaning blade at its edge, it has been tried to cover the edge with a solid fluorine plastic. But this might blunt otherwise sharp edge which is one of the most important properties as a cleaning blade. Also, covering a solid fluorine plastic on a metallic blade and grinding it to obtain a sharp edge has been proposed (e.g. in the Japanese Patent Publication No. 55-77773). But, with this method, the resilience would be poor compared with the rubber cleaning blade. There is also known a method in which a silicone oil having reactive groups at the ends thereof is reacted with an urethane rubber blade (e.g. in Japanese Patent Publication No. 59-15967). In this method, however, the silicone coating tends to gradually peel off with use.
An object of the present invention is to provide a cleaning blade which is excellent in resistance to wear and lubricating and cleaning properties and which allows a copying machine to keep producing beautiful copies semi-permanently.